No limited slip,still modifier?

Hallo everyone in the USA. Mine Limited slip in the dana35 is not working anymore after 16 years. I use always Sunoco 85W140 LS in the diffs.
My question is, do I need still the expensive Friction Modifier init? Or can I leave it out, without problems? Greetings:dunno: :dunno:

I know I had to use the friction modifier that came with the Auburn LSD to get the chatter to stop even though I used Red Line 75w90 with the LS additive in it.